Biosensor analysis systems are known in numerous variants for the detection (quantitative or qualitative determination) of various analytes. For example, the determination of glucose concentration in the blood of diabetics has especially great medical and economic significance. Other important analytes are cholesterol and various blood coagulation parameters. The latter example shows that an analysis parameter in the meaning of the invention is not limited to the concentration of a substance in the sample liquid, but rather the invention also relates to other relevant analysis parameters (in particular in the medical field), such as in this case the blood coagulation time. The invention is not restricted in regard to the analysis parameter.
Biosensor analysis systems are often used in medical laboratories. However, the invention is in particular directed to applications in which the analysis is performed by the patient himself for monitoring his health status (“home monitoring”). For uses of this type, simple handling is especially important to ensure that the required analysis is performed regularly by the patient and the precision of the analytical result is not impaired by handling errors. In addition, the analysis instrument for home monitoring is typically as small, light, and robust as possible. The invention is also suitable for so-called near-patient diagnostics (“near patient testing”).
Elongate plastic strips are typically used as the carrier layer of known biosensors. However, there are also other forms, such as approximately square small plates. At the beginning of the development, biosensors in the form of test strips were typical, whose test fields were produced in single or multiple layers from an absorbent (porous) material, such as paper or porous plastic. A droplet of sample liquid was applied in excess to the surface of the test field. The excess was wiped or washed off. The reaction of the sample liquid penetrating into the test field containing the reagent system (comprising one or more reagent system components) resulted in a change of the color of the test field, which change was analyzed by means of a photometric device contained in the associated analysis instrument.
The present invention refers to electrochemical analysis systems. At the beginning of the development of such biosensors, designs were typical which had a porous test field for applying the sample liquid to its top side. This is, for example, known from U.S. Pat. No. 5,243,516, the disclosure of which is hereby incorporated by reference herein in its entirety. Later, capillary biosensors were suggested, which have a capillary channel, in which the sample liquid is transported from an entry opening by capillary action into a reaction zone, in which the reagent system and the electrodes are located. Early variants of electrochemical capillary biosensors are known, for example, from EP 0170375 A2 and U.S. Pat. No. 5,120,420, the disclosures of which are hereby incorporated by reference herein in their entireties. In the following developmental period, this design principle was applied nearly exclusively for electrochemical biosensors. In particular it was considered advantageous that a capillary biosensor takes up a defined sample quantity which corresponds to the volume of the capillary channel including the reaction zone. This is also referred to as “self-metering”. In addition, capillary sensors were considered advantageous with respect to their handling, because it suffices to bring a blood droplet, e.g. generated on the fingertip, into contact with the entry opening of the capillary channel, the sample liquid being suctioned rapidly and reliably into the channel. More recent capillary biosensors are described, for example, in U.S. Pat. No. 6,645,359 and WO 2004/068138, the disclosures of which are hereby incorporated by reference herein in their entireties.
The inventors have recognized that capillary biosensors have in many cases limited applicability or cause difficulties in regard to the production and/or handling, instead of the desired simplification. This is true, for example, in the following cases:
a) In many cases it is advantageous to heat the reaction zone of the biosensor, in particular for accelerating the reaction. This allows, inter alia, to use reactants (in particular enzymes) which have superior specificity, but react too slow at room temperature. The heating results in an improvement of the analysis quality and/or a shortening of the required reaction time. Thermostatic control of the reaction zone by means of a temperature measuring device and thermostat control electronics integrated in the analysis instrument, is especially preferred.
The heating device and possibly also the temperature measuring device are advantageously located in the interior of the analysis instrument. However, with typical capillary biosensors, the sample application takes place outside the device. This requires a long capillary channel and therefore a large sample volume. To overcome this problem at least with respect to the temperature measurement, special temperature measuring methods (U.S. Pat. No. 6,880,968, the disclosure of which is incorporated herein by reference in its entirety) and correction methods (WO 2004/090533, the disclosure of which is incorporated herein by reference in its entirety) have been suggested, which allow temperature compensation without temperature measurement. However, these suggestions do not allow heating of the measurement zone.
As will be described below, in embodiments of the present invention a user is able to position the biosensor in the analysis instrument in such a manner that the reaction zone defined by the test field is located at a central position of the analysis instrument in direct contact with a heating device, while still allowing the contacting of the biosensor with the sample to be performed in a very simple manner.
b) Analysis systems which operate with biosensors connected and arranged to form a tape are advantageous in many cases, because they allow in a simple manner the magazine storage of a plurality of biosensors, as well as their transport and positioning in the analysis instrument. It is possible to produce capillary biosensors in the form of sensor tapes and integrate them in corresponding systems (WO 2004/030822 A1, the disclosure of which is incorporated herein by reference in its entirety). However, the production and handling of such biosensor tapes can be made less difficult on the basis of the teachings of the present invention.
c) This is similarly true for multiuse biosensors, which have a plurality of test fields on a flat plate having, for example, approximately the shape of a credit card. Such multiuse test cards are suitable, for example, for applications (as so-called “day packs”), in which the user performs a specific number of analyses daily and the biosensors required for this purpose are positioned on a common support plate. In this context it is again very difficult and complex to use a capillary biosensor.
d) In the field of near-patient testing, it can be desirable to apply a sample to a biosensor's application surface by means of a syringe. With capillary sensors, this possibility for sample supply exists not at all or only with very complex handling.
On this basis, the invention addresses the technical problem to provide a biosensor analysis system which allows easier handling for a plurality of different applications. This object and others that will be appreciated by a person of ordinary skill in the art have been achieved according to the embodiments of the present invention disclosed herein.